The present invention relates to distribution centers for distributing inventory to customers. More particularly, the invention relates to load balancing in distribution centers.
Distribution centers are buildings or regions where inventory is stored and used to fulfill orders for customers. Customers place orders by various modes such as by telephone, mail, Internet browsers, and the like. The enterprise running the distribution center attempts to fulfill as many orders as possible in the shortest amount of time.
A distribution center's “throughput” is defined as the volume of inventory or number of orders fulfilled in a given unit of time. At least two parameters feature prominently in maximizing throughput: (a) useable inventory and (b) load balancing during order fulfillment. Usable inventory simply refers to the amount of inventory that is immediately available for order fulfillment. Obviously, if a distribution center has insufficient inventory to immediately fulfill all its orders, that distribution center cannot realize its potentially highest throughput. Load balancing refers to consistently using all order fulfillment mechanisms available for fulfilling orders. If any of these mechanisms sit idle, throughput drops off rapidly.
A given distribution center may have many order fulfillment mechanisms. In one example, the distribution center includes a conveyor belt that transports a container to various locations, each of which has an order fulfillment mechanism. One location may have a bank of carousels, each containing numerous bins. Each bin holds one or more types of inventory. The carousel moves into a position where items of inventory can be placed in the container on the conveyer belt. Another location may have a few aisles each containing multiple bins. A worker moves through the aisles to pick out requested items and place them in the container. Other types of order fulfillment mechanisms may be employed. The term “pod” will be used herein to describe any and all types of order fulfillment mechanisms. Each pod has one or more types of inventory available for “picking.” Picking refers to the operation of retrieving an item of inventory from a pod and placing it into a container. The container holds the various items that fulfill a given order.
Given that different customers have very different needs and preferences, different orders provide wide and rather unpredictable variation. Optimal load balancing to meet this variation presents a serious challenge. During a given week, for example, several grocery orders may require milk, but only a few of these require anchovies, a few others require spicy tofu, and still a few others require cotton swabs. In fulfilling these various orders, any one of these items could present a throughput bottleneck. Controlling the position and path of a container used to fulfill an order can partially address this problem. However, additional mitigation might result from intelligently distributing or arranging the inventory at specific locations within the distribution center.
The present invention fills a need for better ways to distribute inventory within a distribution center.